1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>Macro BOOST_CONTRACT_OLDOF</title> 5<link rel="stylesheet" href="../../../../doc/src/boostbook.css" type="text/css"> 6<meta name="generator" content="DocBook XSL Stylesheets V1.79.1"> 7<link rel="home" href="index.html" title="Chapter 1. Boost.Contract 1.0.0"> 8<link rel="up" href="reference.html#header.boost.contract.old_hpp" title="Header <boost/contract/old.hpp>"> 9<link rel="prev" href="boost/contract/copy_old_idm46268584750992.html" title="Function copy_old"> 10<link rel="next" href="BOOST_CO_idm46268584725152.html" title="Macro BOOST_CONTRACT_NAMED_OVERRIDE"> 11</head> 12<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> 13<table cellpadding="2" width="100%"><tr> 14<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../boost.png"></td> 15<td align="center"><a href="../../../../index.html">Home</a></td> 16<td align="center"><a href="../../../../libs/libraries.htm">Libraries</a></td> 17<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td> 18<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td> 19<td align="center"><a href="../../../../more/index.htm">More</a></td> 20</tr></table> 21<hr> 22<div class="spirit-nav"> 23<a accesskey="p" href="boost/contract/copy_old_idm46268584750992.html"><img src="../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="reference.html#header.boost.contract.old_hpp"><img src="../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="index.html"><img src="../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="BOOST_CO_idm46268584725152.html"><img src="../../../../doc/src/images/next.png" alt="Next"></a> 24</div> 25<div class="refentry"> 26<a name="BOOST_CONTRACT_OLDOF"></a><div class="titlepage"></div> 27<div class="refnamediv"> 28<h2><span class="refentrytitle">Macro BOOST_CONTRACT_OLDOF</span></h2> 29<p>BOOST_CONTRACT_OLDOF — Macro typically used to copy an old value expression and assign it to an old value pointer. </p> 30</div> 31<h2 xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv-title">Synopsis</h2> 32<div xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv"><pre class="synopsis"><span class="comment">// In header: <<a class="link" href="reference.html#header.boost.contract.old_hpp" title="Header <boost/contract/old.hpp>">boost/contract/old.hpp</a>> 33 34</span>BOOST_CONTRACT_OLDOF(...)</pre></div> 35<div class="refsect1"> 36<a name="idm45988676886832"></a><h2>Description</h2> 37<p>The expression expanded by this macro should be assigned to an old value pointer of type <code class="computeroutput"><a class="link" href="boost/contract/old_ptr.html" title="Class template old_ptr">boost::contract::old_ptr</a></code> or <code class="computeroutput"><a class="link" href="boost/contract/old_ptr_if_copyable.html" title="Class template old_ptr_if_copyable">boost::contract::old_ptr_if_copyable</a></code>. This is an overloaded variadic macro and it can be used in the following different ways.</p> 38<p>1. From within virtual public functions and public functions overrides:</p> 39<pre class="programlisting"><span class="identifier">BOOST_CONTRACT_OLDOF</span><span class="special">(</span><span class="identifier">v</span><span class="special">,</span> <span class="identifier">old_expr</span><span class="special">)</span> 40</pre> 41<p>2. From all other operations:</p> 42<pre class="programlisting"><span class="identifier">BOOST_CONTRACT_OLDOF</span><span class="special">(</span><span class="identifier">old_expr</span><span class="special">)</span> 43</pre> 44<p>Where:</p> 45<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> 46<li class="listitem"><p><code class="computeroutput"><span class="bold"><strong>v</strong></span></code> is the extra parameter of type <code class="computeroutput"><a class="link" href="boost/contract/virtual_.html" title="Class virtual_">boost::contract::virtual_</a></code><code class="computeroutput">*</code> and default value <code class="computeroutput">0</code> from the enclosing virtual public function or public function overrides declaring the contract. </p></li> 47<li class="listitem"><p><code class="computeroutput"><span class="bold"><strong>old_expr</strong></span></code> is the expression to be evaluated and copied into the old value pointer. (This is not a variadic macro parameter so any comma it might contain must be protected by round parenthesis and <code class="computeroutput">BOOST_CONTRACT_OLDOF(v, (old_expr))</code> will always work.)</p></li> 48</ul></div> 49<p> 50On compilers that do not support variadic macros, programmers can manually copy old value expressions without using this macro (see <a class="link" href="boost_contract/extras.html#boost_contract.extras.no_macros__and_no_variadic_macros_" title="No Macros (and No Variadic Macros)"> No Macros</a>).</p> 51<p><span class="bold"><strong>See Also:</strong></span></p> 52<p> <a class="link" href="boost_contract/tutorial.html#boost_contract.tutorial.old_values" title="Old Values"> Old Values</a> </p> 53<p> 54</p> 55<p> 56</p> 57</div> 58</div> 59<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 60<td align="left"></td> 61<td align="right"><div class="copyright-footer">Copyright © 2008-2019 Lorenzo Caminiti<p> 62 Distributed under the Boost Software License, Version 1.0 (see accompanying 63 file LICENSE_1_0.txt or a copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>) 64 </p> 65</div></td> 66</tr></table> 67<hr> 68<div class="spirit-nav"> 69<a accesskey="p" href="boost/contract/copy_old_idm46268584750992.html"><img src="../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="reference.html#header.boost.contract.old_hpp"><img src="../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="index.html"><img src="../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="BOOST_CO_idm46268584725152.html"><img src="../../../../doc/src/images/next.png" alt="Next"></a> 70</div> 71</body> 72</html> 73
